Prediction of Metal Remobilization from Sediments under Various Physical/Chemical Conditions "Design of Experiment for Cd & Co"

Date of Award

5-2015

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Dr. Eid Alkatib

Abstract

Summary: Trace/heavy metal contamination is a major threat to our water supplies. It is highly important to understand the remobilisation mechanisms of the different metals under different conditions. The metal partition coefficient Kd (L/kg) describes the ratio of sorbed metal concentration in the solid phase m (mg/kg) to the dissolved metal concentration at equilibrium. The metals can be present in many different species with different solubility. The formed species are affected by wide range of factors which are interconnected and no dominant process can be determined in most cases. Both organic and inorganic matters content type an concentration in sediments, pH, and salinity are the main factors that influencing the speciation and the partitioning of metals. In this work, the partitioning of the two transition metals Co and Cd was examined under different values of Ph, salinity and organic matter content concentration. Experiments are evaluated to investigate the effect of all three factors. Three levels of organic matters are tested against five levels each of pH and salinity. The MiniTab16® statistical software program was used to generate the order of experiments. It was shown, that pH has high impact on Kd for Co and even higher for Cd. In particular, the partition coefficient increased with pH until 7.2. After this point the partition coefficient increased drastically. This was explained by the formation of almost insoluble Co(OH)₂ and Cd(OH)₂ species increasing drastically the insoluble metal content. High dependence of Kd on the organic matter content at zero salinity was observed. Multiple regression equations were generated to predict Kd for both metals under various conditions. It was concluded that the methodology can provide important relationships between the investigated factors and Kd and can highlight unexpected symptoms of the system. On the other hand, some drawbacks of the methodology were also emerged which should taken into account in future studies.

Comments

Master's thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Chemistry in Sacred Heart University.

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